Recently, an oxide semiconductor has been extensively studied in replacement of a typical silicon based semiconductor. Zinc oxide, indium oxide, and gallium oxide based single, binary and ternary compounds have been reported for the oxide semi-conductor. Besides that, a zinc oxide and tin oxide based binary compound has been studied. For a thin film formation technique using an oxide semiconductor material, various methods such as a vacuum evaporation deposition method, a sputtering method, a chemical vapor deposition method, a spray method, and a solution process method (a sol-gel method) have been studied.
A deposition method using a solution process as an alternative of an expensive vacuum deposition method may not require expensive equipment and is also recognized as promising method for directly forming a thin film as required without an additional patterning process on a large area.